Autism Spectrum Disorder (ASD) is a complex group of behavioral disorders characterized by defects in social interaction and communication associated with restricted and repetitive behaviors and activities. The prevalence in pediatric age is continuously increasing in Western countries (58-67 / 10,000). The Diagnostic and Statistical Manual of Mental Disorders version 5 (DSM-5) describes a worldwide population prevalence of approximately 1%. According to the latest data from the National Observatory for the monitoring of ASD, in Italy 1 child out of 77 (age 7-9 years) has the disease with a higher prevalence in males: males are affected 4.4 times more than females . The clinical manifestations of ASD are the result of complex interactions between genetic, epigenetic, environmental and microbiological factors. Alterations in nutritional status, eating habits and adverse reactions to food appear to be more frequent in children with ASD. It is estimated that 46-89% of children with ASD have feeding problems which can include unusual eating patterns, rituals and food selectivity. These types of eating behaviors can lead to severe alterations in nutritional status. Furthermore, the data present in the literature concerning the eating habits of children with ASD suggest a high consumption of "junk food" and foods rich in calories together with a refusal of fruit, vegetables or proteins. These data suggest that the dietary and behavioral problems frequently present in these children could favor a condition of obesity. Finally, a high percentage of children with ASD undergo elimination diets, characterized by exclusions of foods relevant to the diet of a child such as milk and gluten to alleviate the symptoms of the disease. Such elimination diets are only rarely supervised by a nutritionist with further consequences on nutritional status.

Inclusion Criteria:

• diagnosis of autism spectrum disorders

Exclusion Criteria:

• Age at enrollment <24 or> 48 months.
• Concomitant presence of other chronic diseases
• epilepsy,
• neurological syndromes,
• immunodeficiencies,
• diabetes,
• congenital heart disease,
• autoimmune diseases,
• inborn errors of metabolism,
• tuberculosis,
• cystic fibrosis,
• chronic respiratory tract diseases,
• inflammatory bowel disease,
• celiac disease,
• eosinophilic pathologies of the gastrointestinal tract,
• functional gastrointestinal disorders,
• obesity,
• tumors,
• malnutrition • Major malformations or previous surgery of the gastrointestinal / urinary / respiratory tract.